The SAMI Galaxy Survey: trends in [α/Fe] as a function of morphology and environment

• Published in: Monthly Notices of the Royal Astronomical Society
• Main Authors: Watson, Peter J., Davies, Roger L., Brough, Sarah, Croom, Scott M., D’Eugenio, Francesco, Glazebrook, Karl, Groves, Brent, López-Sánchez, Angel R., van de Sande, Jesse, Scott, Nicholas, Vaughan, Sam P., Walcher, Jakob, Bland-Hawthorn, Joss, Bryant, Julia J., Goodwin, Michael, Lawrence, Jon S., Lorente, Nuria P. F., Owers, Matt S., Richards, Samuel
• Other Authors: Swinburne University of Technology
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Oxford University Press (OUP) 2021
• Subjects: Hubble; sami
• Online Access: http://hdl.handle.net/1959.3/465884; https://doi.org/10.1093/mnras/stab3477

We present a new set of index-based measurements of [alpha/Fe] for a sample of 2093 galaxies in the SAMI Galaxy Survey. Following earlier work, we fit a global relation between [alpha/Fe] and the galaxy velocity dispersion sigma a for red sequence galaxies, [alpha/Fe] = (0.378 +/- 0.009)log(10) (sigma/100) + (0.155 +/- 0.003). We observe a correlation between the residuals and the local environmental surface density, whereas no such relation exists for blue cloud galaxies. In the full sample, we find that elliptical galaxies in high-density environments are a-enhanced by up to 0.057 +/- 0.014 dex at velocity dispersions sigma < 100 km s(-1),compared with those in low-density environments. This alpha-enhancement is morphology-dependent, with the offset decreasing along the Hubble sequence towards spirals, which have an offset of 0.019 +/- 0.014 dex. At low velocity dispersion and controlling for morphology, we estimate that star formation in high-density environments is truncated similar to 1 Gyr earlier than in low-density environments. For elliptical galaxies only, we find support for a parabolic relationship between [alpha/Fe] and sigma, with an environmental alpha-enhancement of at least 0.03 dex. This suggests strong contributions from both environment and mass-based quenching mechanisms. However, there is no evidence for this behaviour in later morphological types.